Impregnation with tin for strong oxidative dehydrogenation catalysts

ABSTRACT

A TIN/PHOSPHORUS/GROUP IA OR IIA OXIDATIVE DEHYDROGENATION CATALYST, SUBSEQUENT TO HEATING, IS IMPREGNATED WITH ADDITIONAL TIN AND THEN IS HEATED TO IMPROVE THE PHYSICAL INTEGRITY OF THE CATALYST.

Patent Office 3,687,868 Patented Aug. 29, 1972 3,687,868 IMPREGNATIONWITH TIN FOR STRONG OXIDA- TIVE DEHYDROGENATION CATALYSTS Emory W.Pitzer, Bartlesville, Okla., assignor to Phillips Petroleum Company NoDrawing. Filed June 22, 1970, Ser. No. 48,543 Int. Cl. B01j 11/82.

3. Cl. 252-435 5 Claims ABSTRACT OF THE DISCLOSURE A tin/phosphorus/Group Ia or IIa oxidative dehydrogenation catalyst, subsequent toheating, is impregnated with additional tin and then is heated toimprove the physical integrity of the catalyst.

This invention relates to an improved oxidative dehydrogenationcatalyst. In another aspect, this invention relates to a process for theproduction of an improved oxidative dehydrogenation catalyst.

ltieretofore, oxidative dehydrogenation catalysts have been formed fromphosphoric acid and tin oxide. These catalysts were improved by formingthe oxidative dehydrogenation catalysts from a phosphorus-containingmaterial, a tin-containing material, and a Group Ia or Ila metal ormetal-containing material.

it now has been found that these oxidative dehydroger ation catalystsare improved by heating the catalysts,

impregnating the heated catalysts with tin or a tin-con-.

tait'ing material to provide the catalysts with 0.25 to wei :ht percentof additional tin based on the weight of the initial catalyst, andheating the thus-treated catalysts.

The process of this invention provides a novel catalyst with improvedphysical integrity, i.e., improved physical stre agth. Such a catalystwill have a longer life in conven ional catalytic reactors. Further, thethus-treated catalyst is less susceptible to pulverization duringhandling or shipping.

The thus-treated catalyst is useful for oxidatively dehydrogenating avariety of hydrocarbons, for example, olefins such as alkenes, andcycloalkenes and the like.

Accordingly, it is an object of this invention to provide a process forthe production of an oxidative dehydrogenation catalyst.

Another object of this invention is to provide an oxidativedehydrogenation catalyst.

Other objects, aspects and advantages of this invention will becomeapparent to one skilled in the art upon consideration of the disclosureand appended claims.

Substantially any phosphorus, tin, and Group Ia or 'IIa containingmaterials can be employed in preparing the catalyst to be treatedaccording to this invention so long as at least one of the materialsused contains oxygen, none of the materials is deleterious todehydrogenation catalytic effects, and all of the elements in thematerials used other than phosphorus, tin, oxygen, and Group Ia or IIametals are volatilized by heating the catalysts to at least thetemperature at which the catalyst is used, e.g., 1000 F., or are removedby washing the catalyst, e.g., with water.

Suitable phosphorus-containing materials employed to prepare thecatalyst include, besides phosphoric acid, phosphorus pentoxide, thephosphorus halides, and the Group Ia and 11a metal phosphates such aslithium phosphate, sodium phosphate, potassium phosphate, rubidiumphosphate, cesium phosphate, magnesium phosphate, calcium phosphate, andthe like. Other phosphorus-containing materials that can be employed toprepare the catalyst to be treated according to this invention areammonium phosphate and mono-and dibasic phosphates of ammonia and ofGroup Ia and 11a metals such as lithium monobasic phosphate, sodiumdibasic phosphate, beryllium dibasic phosphate, magnesium dibasicphosphate, barium mono basic phosphate, ammonium phosphate, ammoniumdibasic phosphate, and the like.

The tin materials employed to prepare the catalysts to be treatedaccording to this invention include any such material soluble ordispersible in water, alcohol, or ether, and include both stannous orstannic compounds. Representative examples of suitable tin compoundsare, for sake of brevity, given only as the stannic compound but it isto be understood that the corresponding stannous compound is equally asapplicable. Representative examples include stannic halides (stannicfluoride, stannic chloride, stannic bromide, stannic iodide), stannicsulfate, stannic acetate, stannic oxide, stannic tartrate, and stannicnitrate. The tin materials employed to prepare the catalyst to betreated according to this invention and in the impregnation step can bethe same or different tin compound.

Besides elemental Group Ia or Ila metals, Group Ia or Ilametal-containing materials that can be used include the nitrates, thehalides, the sulfates, the oxalates, the acetates, the carbonates, thepropionates, the tartrates, the bromates, the chlorates, the oxides, thehydroxides, and the like.

The phosphorus-containing materials, the tin-containing materials, andthe Group Ia ir Ila metal or metal-containing materials can be combinedin any conventional manner which will yield catalytic combinationssuitable for oxidative dehydrogenation processes. For example, thecatalyst components can be combined using a coprecipitation technique asdisclosed in detail hereinafter in the specific examples, byconventional aqueous or nonaqueous solu' tion or suspension mixing, byion exchange, by simply mixing the components by themselves without theuse of additional solvents, and the like including combinations of thesetechniques.

Generally, the catalysts can be formed by mixing the components forperiods varying from about 1 minute to 5 hours in the presence orabsence of a solvent or dispersant, at temperatures from about roomtemperature up to about 200 F. Ambient, sub-ambient, or super-ambientpressures, and ambient or inert atmospheres such as nitrogen, and thelike can be used.

Suitable solvents or dispersants that can be employed for the combiningof the catalyst components include water, alcohol, or ethers for thestep of combining the tin compound and phosphorus compound, and thesesolvents as well as hydrocarbons, halogenated hydrocarbons, ketones,esters, and the like for any other steps of the catalyst preparation.

The catalyst itself when finished and in a condition for treatmentaccording to this invention will contain from about 0.1 to about 16weight percent phosphorous, from about 15 to about 75 weight percenttin, and from about 0.1 to about 10 weight percent Group Ia and/or Ilametal, preferably 0.1 to weight percent, all weight percentages beingbased upon the total weight of the final catalyst. The amounts ofphosphorus, tin, and Group Ia and/ or IIa metal present in the finalcatalyst total less than 100 percent of the catalyst, the differencesbetween the total and the 100 percent being substantially combinedoxygen in sufiicient amount to satisfy the valence requirements of theGroup Ia and/or IIa metal, tin, and phosphorus.

A presently preferred method of preparing the catalyst to be treatedaccording to this invention is to mix solutions or suspensions of, forexample, the phosphates and/or phosphoric acid, one or more tincompounds, one or more Group Ia and/or IIa metal or compound, and atleast one of ammonia, ammonium hydroxide, sodium hydroxide and potassiumhydroxide, filter, wash to remove any undesirable electrolytes, dry, andcalcine. An agglomeration step such as pelletizing, extruding, orpilling, can precede or follow the drying step or calcining ste Theconcentration of the various solutions that can be used to make thecatalyst to be treated according to this invention can vary widely,e.g., from about 0.01 to about molar or more, depending on thesolubility of the particular materials employed. Any order of mixing canbe used, and the final pH of the mixture is generally in the range offrom about 2 to about 10, preferably from about 3.5 to about 6.5. Theprecipitate that forms is separated from the liquid by any conventionalmeans such as filtration. Thereafter the precipitate is washed withdilute aqueous ammonium salt solutions such as ammonium acetate,ammonium nitrate, ammonium sulfate, and the like, and/or with deionizedwater to remove electrolytes. The washed precipitate is then dried forfrom about 2 to about 24 hours at temperatures of from about 100 toabout 300 F. in air or an inert atmosphere such as nitrogen. The driedprecipitate is then calcined from about 1 to about 24 hours at fromabout 600 to about 1300 F., preferably at about the temperature at whichthe catalyst is to be used in the dehydrogenation process, under ambientor inert atmospheres. As mentioned before, an agglomerate-forming stepcan precede or follow the drying or calcining step. The dried andcalcined catalyst is preferably formed into 4 to -inch pellets bycompression molding or extrusion, or is simply screened to a desiredsize, such as 10-28 mesh (Tyler Sieve Series, Mechanical EngineersHandbook by L. S. Marks, 4th Edition, McGraw-Hill Book Co., Inc., N.Y.,1941, p. 836). Optimally a particulate tin/phosphorus/ oxygen materialis formed, and the Group Ia and/or Ila metal-containinag compound orcompounds is added by, for example, impregnation followed by drying.

By this invention, these oxidative dehydrogenation catalysts are treatedby (a) heating the catalyst to 600 to 1300 F., preferably 1100 to 1200F., (b) impregnating the heated catalyst with a tin-containing materialto provide the catalyst with 0.25 to 10 weight percent of additionaltin, and (c) heating the treated catalyst at temperatures in the rangeof 600 to 1300 F., preferably 1100 to 1200 F., in the presence of anoxygen-containing atmosphere.

Generally, the heating of step (a) is carried out for a time rangingfrom 1 to 24 hours. The heating of step (c) is carried out for a timeranging from 1 to 24 hours. If desired, the heating of step (a) can bethe final heating step of the original preparation of the oxidativedehydrogenation catalyst to be treated according to this invention.

The impregnation step can be carried out with any tincontaining materialwhich is converted by the subsequent heating step in anoxygen-containing atmosphere to tin oxide. For example, tin compoundssuch as stannous sulfate, stannic sulfate, stannous nitrate, stannicnitrate, stannous acetate, stannic acetate, stannous tartrate, stannictartrate, and the like can be employed. Preferably, stannous sulfateand/or stannic sulfate are employed.

The improved catalysts of this invention can be used in any conventionaldehydrogenation, particularly oxidative dehydrogenation, process usingconventional procedures and techniques. Suitable oxidativedehydrogenation processes are those which dehydrogenate at least onematerial selected from the group consisting of alkenes, alkadienes,cycloalkenes, alkylpyridines, and alkyl aromatics, using an elevatedtemperature, and a molecular oxygen-containing gas, with or without thepresence of steam. The alkenes and alkadienes can contain from 3 to 10,preferably 4 to 6, carbon atoms per molecule, inclusive, and thecycloalkenes can contain from 4 to 10, preferably 4 to 6, carbon atomsper molecule, inclusive. The alkylpyridines and alkylaromatics cancontain from 1 to 4, preferably 1 to 2, alkyl groups per molecule whichthemselves contain from 1 to 6, preferably 4 to 6, carbon atoms pergroup, inclusive, with at least one alkyl group having at least 2 carbonatoms.

The advantages of this invention are further illustrated by thefollowing examples. The reactants and the proportions and other specificconditions are presented as being typical and should not be construed tolimit the invention unduly.

EXAMPLE Catalyst preparations Catalyst l.-Aqueous solutions of stannicchloride and phosphoric acid were mixed and reacted with ammoniumhydroxide to give a precipitate. The precipitate was filtered and washedessentially free of chlorine by resuspension in water and refiltering.The washed precipitate was spray-dried, mulled with about 5 percentwater, extruded to an extrudate inch in diameter and about inch inlength, and dried. The dried extrudate was impregnated with an aqueoussolution of lithium nitrate to give the final desired composition. Theimpregnated extrudate was dried and calcined at 1100 F. in air for about4 hours as the final preparation step. The final catalyst contained 10percent phosphorus (22.9 percent P 0 and 58.4 percent tin (73.9 percentSnO The final composition also contained 1.5 percent lithium (3.2percent Li O).

Catalyst 2.-Catalyst 1 was impregnated with an aqueous solution ofstannous sulfate, dried, and calcined in air at 1100 F. for 16 hours.The solution used to impregnate contained 3.6 grams of SnSO in ml. ofsolution. The tin content was increased to 59.4 weight percent ascompared to Catalyst 1 which contained 58.4 weight percent tin. This wasan inventive catalyst of the invention.

Catalyst 3.--Catalyst 1 was impregnated with an aqueous solution ofstannous sulfate, dried, and calcined in air at 1100 F. for 16 hours.The solution used to impregnate contained 7.2 grams of SnSO in 100 ml.of solution. The resultant tin content was increased to 60.4 weightpercent in this inventive catalyst.

Catalyst 4.Catalyst l was impregnated with an aqueous solution ofstannous sulfate, dried, and calcined in air at 1100 F. for 16 hours.The solution used for impregnation contained 14.4 grams of SnSO, in 100ml. of solution. The resultant tin content was increased to 62.4 weightpercent in this inventive catalyst.

Catalyst Testing I Physical strength (pounds of pressure required tocrush extrudates) as well as catalytic activity for dehydrogenation ofbutenes to butadiene are:

heating the impregnated composite at a temperature ranging from about600 to 1300 F., thereby preparing an oxidative dehydrogenation catalyst.

2. The process according to claim 1 wherein the heat- 1 Conditions:Butene space velocity=300; air space velocity=l,200; steam spacevelocity: 6,000; sample time in the dehydrogenation period=3 hours;pressure=atomospheric; quartz reactor; 7 mm. internal diameter; 3-4 incatalyst depth; 34 cc. of catalyst; product determination by gas liquidchromatography.

Norm-Space velocity is vol of gas/vol. of catalyst/hr. at STP.

N o'rE.Yield=Mole percent of butenes converted to butadiene,single-pass. Modivity= Selectivity to butadiene based on gas-phaseproducts only.

The above data demonstrate that the catalysts of this invention performas well as or better than the catalysts of the prior art. Further, thecatalysts of this invention clearly have improved physical strength overthe catalysts of the prior art.

Reasonable variations and modifications are possible within the scope ofthis disclosure without departing from the scope and spirit thereof.

I claim:

1. In a process for the production of an oxidative dehydrogenationcatalyst which is a calcined composite of P/Sn/O/and at least one GroupIa or Group IIa metal, said composite comprises,

about 0.1 to 16 weight percent phosphorus, about to 75 weight percenttin, and about 0.1 to 10 weight percent Group Ia or Group Ha metal, saidoxygen being present as combined oxygen,

wherein the improvement comprises impregnating said composite with afurther tin containing material suflicient to provide said compositewith about 0.25 to 10 weight percent of additional tin, said further tincontaining material is a tin oxide or tin containing materialconvertible to the oxide on heating in an oxygen containing atmosphere,and

References Cited UNITED STATES PATENTS 3,501,547 3/ 1970 Nolan et a1252--437 X 3,513,215 5/ 1970 Ogle 260680 E 3,555,105 l/1971 Nolan et al252437 X PATRICK P. GARVIN, Primary Examiner US. Cl. X.R.

